Primitive Archer
Main Discussion Area => Bows => Topic started by: Dane on May 02, 2008, 05:25:04 pm
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Man, I hope this works. Last few times I tried to post photos, nothing but problems.
Some of you may recall the manuballista I am building. Essentially, the woodwork is done on that, and I will continue the thread once I get the bronze casting done.
In the meantime, here is a second machine, a much more powerful one with 2" springs and firing 18" arrows, at what I estimate will be 1,000 pounds of pull. The maximum range of this machine maybe around 250 to 300 yards, but effective range will probably be in the area of 100 to 150 yards. As you can clearly see, the machine is far from complete, and once I chisel out the last two double moritises for the two inner stancions, I can glue it together, true up all the sides, and then sheath the frame in steel, which is already cut but not drilled for bolts or rivets, one of two ways I will attach the metal sheathing. It is critical that the basic jointry be as strong as I can make it, as safety is clearly a factor. If you have had a bow explode, you know how exciting that is. If one of these explodes, it can be ugly. :)
I expect this machine to be ready for testing in mid to late summer. The manuballista will come sooner.
Attached too is a Google SketchUp drawing of the machine. It is a free program, and a lot of fun, as well as useful. Davenport the Pug is helping out in showing size comparisons. I'm goint to post pictures one at a time, so forgive me. I have yet to get my picture act together.
Dane
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Another shot, this one of myself holding the spring frame. Henry's Tacos is awesome, and if you are ever in my old neighborhood, go there :)
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As you can see, I still have to finish two tenons, and then true up everything. It looks rougher with the digital camera flash then in person. The area you see chiseled out on the inner sides of each counter or inner stanchions will be where the case and dovetailed slider fit into the machine. I'm casting a bronze frame and pin to pin the entire case assembly together, as was done with a machine found in the 19th century in Caminreal, Spain. The entire machine, then, will break down for easy assembly and disassembly in field or battlefield conditions.
If all of this is confusing, I've been carefully documenting the entire design and building process, and will eventually post a thread so you can see how the project goes, including testing.
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Here is a in-progress drawing of the trigger assembly. I am designing it to be cast and bolted to the slider. I suppose the parts can be forge welded as well, not sure, but my blacksmith will advise me. These parts will be cast from bronze, as I don't have iron working skills and want to do as much as I can myself, and keep the work as close to the practices (as far as we can tell 2,000+ years later) of the ancient world as possible.
The design I am working on closely follows Heron's (a Greek engineer) description of a cheiroballistra trigger. The cheiroballistra is a very advanced iron-framed machine depicted on Trajan's Column, and is the last major development in torsion-powered war machines from the classical period. The wooden ones I am concentrating on are much earlier designs, but it is assumed they were used wiell into the Empire period.
These parts are for my smaller manuballistas / scorpio-minors / small or lesser scorpions, but will be easily adaptable for use on the larger 2" machines, as well as a future gastraphetes, or belly bow, which is on my future list of projects to undertake. Notice the use of a linear or sawtooth ratchet on the sides of the weapon's case. This was, to the best of my knowledge, a system favored by the Greeks, the Romans having introduced the circular ratchet. The 2" machine will use the circular ratchet system, while the hand held machines will use the earlier linear ratchets.
By the way, if anyone feels that these arrow firing machines do not belong in PA (I myself debate whether this constitutes primitive archery as we think of it, but do feel it does), let me know, and I'll quit posting about them.
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very cool, looks a little heavy for hunting though.. ;D ;) Hawk
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Thanks, Hawk. You'd only use these for killing humans, of course. They were powerful enough to penetrate any known armor and shields of 2,000 years ago.
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cooooooollll ya gonna bring one down this year to test fire on the range
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Hi Jamie. Thanks man. I am really looking forward to this year's event. First weekend in June, yes?
I will bring the machines, even if I don't have them finished. Wish they were, but the death of my dad and a few other things set back my schedule quite a bit. I'm still trying to get back into my normal routine in some respects.
Dane
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looking forward to havin ya come down again. very sorry to hear about your father. peace
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Thanks, Jamie. It will be great to go back to your club and hang out and learn how to / make primitive stuff. Thanks about my dad. We die because we live.
Dane
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looks like a good security system >:D!!!
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Lol. If a burglar was caught at the wrong end of these machines, he would find himself pinned to a wall through his spinal column. Serve him right too.
Dane
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Happily, the mortise and tenon work on the spring frame (capitulum in Latin) is behind me. There are a total of 16 mortises, 8 on each of the two hole carriers (tabula, the top and bottom parts of the capitulum with the 2" holes bored through them for the rope springs). It was very enjoyable making these (I found that working with a wooden mallet and chisels is really relaxing mentally, and the world fades away as it is just me and the project in the shop. You know what I mean, I think), though I am glad I am finished with them, as well. This skill will come in handy in a variety of ways in the future, I'm sure.
Dane
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One more shot, illustrating the mortises and tenons.
Dane
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Oh, sorry about the double photo posting. I edited the post, and thought I had to re-attach the image.
Dane
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One more image, if I can be so bold. This is the drawing I've been working on for the trigger assembly for the manuballista, or small scorpion. I'm happy with this particular effort, and will now make the patterns to cast the components. Bronze will be more than strong enough for these parts, though if I was builiding a large stone throwing ballista, I'd want these made from iron or steel.
You can see the linear Greek-style ratchet on the side of the machine. The pawls, one on each side of the wooden slider, will engage the ratchet as I lean my weight on the machine, thereby spanning or cocking the machine. With the 2" inch scorpio, there will be a winch assembly at the end of the machine. Much more power, and a much better system in this instance.
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For those who are interested, I've done a lot more work on the machine, and it is starting to look like a catapult.
The case is completed, which is the part with the dovetail groove that the wooden slider will fit into, which has a groove at top for the arrow, and slides up so that the pawls on the trigger assembly can hook over the bowstring. The winch cheeks are glued on, but still have to be pegged for exta strength. The bronze circular ratchet will be placed there, as well as another pawl, which will engage the ratchet as you crank back the machine to full draw.
It weighs in at 17 pounds right now, but will weigh more later, after I rivet on the steel plating for the spring frame, and fit on the other metal parts at the rear.
Dane
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Here is a shot of myself standing next to the catapulta. It it about 5' long.
Dane
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Last, here it is sitting a bit lamely on the stand I had build a few months back. I won't be actually making and fitting on the universal joint, which allows the piece to travers and elevate, until the spring frame is entirely done, to make sure I find the exact fulcrum point, so the machine sits perfectly level and doesn't droop foward of backwards. If it doesnt look quite in scale, you are correct. The stand was concieved for a 4" machine. I plan to make a smaller center column, and mortise in the legs and cross pieces, which I don't need to alter in any way for that to work. The larger column I can set aside for some future project, or just as a very heavy paper weight.
Dane
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That's one wild machine Dane ;D. I wanna see it done along with some pic's of the damage it's done - bet you do too huh :)..
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Thanks Paul. The whole point really is the damage the machine can inflict! I'll be taking viido when I run the tests, and will post it here. Pumpkins, watermellon, 3D targets, all will die. :)
I was having a discussion of arrow firing macihnes with a guy who runs the local concertina store (we do have one, strange to say). He asked me why the Romans would field 60 or so of these machines with a legion on campaign, and I had to tell him the entire point of engaging the enemy was to destroy him completely. He didn't quite get it.
Dane
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I need one of these in the backyard, would really make the neighbors wonder ;D
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lol, Dana. I was thinking of mounting the machine in the back of a pick up and then driving into Manhattan. No more long lines to worry about at Starbucks.
I have this annoying old neighbor, Ivan. He spends many hours in his folding chair staring at nothing, day in and day out, and spying on everyone. His garage is next to mine, so he is out there often when I'm working in the shop area. He of course has no idea what I'm building, which is probably a good thing. I am certain there are no laws on the books about building artillary in your garage, but you never know.
Dane
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Well, for those of you still interested in this tomfoolery, much has been done with the catapults.
Here is a shot taken last month in Vermont at a living history timeline event. Sure, I am dressed as an auxilia archer rather than a legionary (hint: the uncouth trousers and long sleeved tunic gives me away as a crude barbarian, but I made all the clothing myself out of linen, uncouth or not). The scorpio is clamped to the stand temporarily using a hand screw, as I have to wait unti it is plated, strung, and all the other parts completed to find the exact fulcrum point for the universal joint.
I've recently gotten good at hand forming copper rivets using a heavy ball peen hammer and lots of sweat, and will be cutting out, drilling, and bluing / blackening 16 guage mild sheet steel to plate the spring frame over the coming week. This will simulate Roman hand forged iron plating, which was hand hammered until flat, then heated up in the forge, fat was rubbed on, and it was polished with fiber waste. This weekend, I'm making a primitive anvil using a large sledghammer head turned up end and embedded into a log. It will come in handy for pounding sinew and other jobs, as well. Bob Patrick, a member of PA boards, has been an amazing partner and inspiration throughout this process, and I clearly would not be nearly where I am or be able to produce such qulity without him. His hand forged nails he has provided to me are absolutely beautful. Shots of those will come when they are installed.
I simulated one rope spring using poly rope, to try out some ideas. I ended up using about 75 feet of rope for one spring, so I expect this machine will take about 150 to 200 feet of horsehair rope. The small scorpio-minor (his name is "Sharp Little Teeth") sitting on the ground will take considerably less.
I have 18 pounds of bronze in transit right now, so I am nearly ready to begin casting all bronze parts for both machines.
I also have some red milk paint, and expect the machines will look handsome in dark red and yellow, with bronze and steel ratchet, washers, etc.
I expect to have the machines both done within 3 months, and then the fun begins.
Dane
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Wow! Will you sell the plans to build them. I think I could really go for the smaller one. Looks hand portable!
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That's a fine piece so far , keep up the good work, I can't wait to see it flingin arras.
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Maybe you can do a penetration test on Ivan's Car, like the drivers side door with ol' Ivan sitting in the drivers seat! ;D
That would keep him from staring non-stop....
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when can we see it shoot? >:D
SJM
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Great stuff Dane, thanks for sharing with us eh :)
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Thanks, everyone.
YewArcher, as soon as it is ready to begin shooting tests, I'll be documenting it with video as well as still shots, and will post those here of course. I exepect maybe 3 months, but maybe a bit longer. For certain, before the end of the year. Same with Sharp Little Teeth.
D Tiller, I can help you out in designing and building your own machine. I recently came across references from Philon that there were very tiny arrow shooting machines, some as small as a 1/2 span, which means they shot 4.5 inch long arrows or darts, and had 1/2" diameter springs. That is even smaller than the scorpio-minor. No one has found one yet, but only one small wooden framed catapult has ever been found, as well (the Xantan machine I used as a point of departure to develop the scorpio-minor). Much has been lost in 2000+ years.
Dane
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Dane- That is really cool. I want to make one too, but I don't have any knowledge of the metal working aspect. But for now I am working on other things.
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Thanks Dane! I think that small one you mentioned would be aw some to try to build. It seems to me they must have used smaller man portable machines for sniping purposes. Precursors to the crossbow?
I know the Greeks built a smaller version that you used your body weight to cock the Ballast with. I have to think there must have been a greater advantage to using these than a bow but don't know what it could be. Longer range? Better penetration? Able to carry more bolts than arrows?
Dane do you happen to know what animal the sinew came from for these weapons? I have a feeling that the modern machines I have seen built with Dacron are lacking in potential due to the artificial nature of the rope being used. Plus, there is a stretch and return factor with animal hair or sinew that you don't get with Dacron or other modern materials. I bet it reduced wear and tear on the engine and increased the distance and speed with which the bolts would fly. Do you think this is possible Dane?
Question, do you think they used a ratcheting system with the small hand portable machine? I have a feeling it was more of a physical body effort with the smaller ones.
David T
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Thanks, Orcbow. I started these projects with zero metal working skills. Like bow making, I wanted to learn, so I had to decide to learn the necessary metal skillls. They are pretty rudimentry, really. Casting is not impossibly hard to learn, and I made myself a small propane fired melting oven, basically a metal cylinder on end lined with refractory and using a commercial bbq tank with a high-volume regulator and hose so I can get the needed psi to get it to 1800 degrees. Hand made rivets are not that easy, but not too hard either, mostly using a heavy ball peen hammer carefully to flatten the shank ends, then peening the edges around and down onto the sheet metal. As for hand forged nails, my blacksmith friend is helping, though I want to learn to smith one day. I just picked up an antique anvil today, cheap! Found it in a dingy little antique store near me. More than large enough (I can barely lift it), and it is probaly American, German, or English made, so good quality.
Posted are two shots of my first ever bluing. This is to simulate the way actual sheet iron would have looked as done by the Romans. I used Vans bluing, easy and fun to use. The part you see is an inner spring frame stanchion. I am plating all the frame parts, and it will weight quite a bit more when it is done. One day, I want to builld one of these machiens using reproduction ancient Roman and Greek hand tools only, only using the same processes that would have existed 2000 year ago, such as chiseling out the various holes, no power drills, etc.
Dave, I appreciate the interest! The Greek belly bows, called gastrophetes, really are the first true catapults. If you look at that shot of me at the Vermont event, you can see the scorpio-minor (lesser or small scorpion) on the ground, the one I had been posting about a while back. It cocks by using your weight on the back horizontal brace, leaning forward to the slider is against the ground or a handy wall, say, and your weigh spans the machine. I am making it using the Greek style linear ratchets, you can see the SketchUp drawing I did a while back during the design phase. The advantage is that you can fire an arrow with a hand held machine that is much stronger than the strongest self or composite bows, and the trajectory is very flat, and so fast you literally can not see the bolt coming at you, unlike a bow. These things are supposed to be so powerful, they can defeat any known armor of the day, and easily punch through chain mail with heavy arrow tips, very similar to the medival bodkins. As well, it is much easier to train a man to use this than to use a war weight bow, as we all know. It took a life time to get proficient with a heavy war bow.
The gastrophetes used, we think, a composite bow, so it is similar looking to a cross bow, but much heavier, much earlier than even the first wimpy little cross bows.
As for sinew, that is the holy grail for modern catapult builders! You need so much sinew, no one has tried, until now. Even Dr. Schramm, one of the great early pioneers of bow reconstructing failed in this area. I dont yet know how much sinew would be needed for 150 feet of rope, what I will need for the 2" machine, let alone the amount for a large balista, which has huge springs. You are right, almost every single interpreted catapult has used dacron rope. It is not the best solution, but used frequently. Horse hair rope is a good second string material, though, and what I am using until I can acquire the amount of sinew I need for future projects.
How Vetruvius described creating the rope springs is that the engineer build a special small winding mechanism, and then pluck the sinew rope at regular intervals, to determine that he has equal tension throughout the processes. All anyone knows now is that real sinew rope would be incredibly effective, and we can learn too the disadvantiges of using that materil in the field, such as during damp weather, things like that.
I doubt they used ratchets with the small machines. My thoughts are that about 1.5" and up for spring diameter, you need a winch system of some sort to span the machine. The gastropetes and my little machine will use body weight, and it simplfies construction considerably.
Dane
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Are there any pictures or ancient diagrams or text describing the smaller ones?
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Alas, no, only literary reference. They would certainly have followed the standard formulas developed by the Greeks and perfected by the Romans. I'll post that formula tomorrow; with it alone, you can design any machine you want based on desired spring size / arrow length, from a tiny dart to a 3' long mutant bolt of doom that would plow through the front ranks of the enemy and continue to travel along, it had so much energy.
The most valuable manuscripts we have were written by four engineers; Philon, Vitruvius, Heron of Alexandria, and Biton. The illustrations are often missing from some texts, and all are badly corrupted by copiest over the centuries, so much is still conjecture. Later, I'll post some, so you can see what I mean. They show all perspective at once, hard to describe, and worse to puzzle out.
If you are really serious about all this, you will find it as addictive in it's way as bow building. I have, anyway. And performance-wise, no bow of any kind, or crossbow for that matter, can come close to what these machines can do. Even the great English war bow seems tiny in comparision, as do the mighty asiatic composites. They dominated ancient battle fields for 1,000 years, so they must have been pretty good :) And another facinating thing about catapults is that they are the best documented and understood ancient machines.
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I am as intrigued as I am lost. What springs??? How does it work (in layman's tongue) ???
I like how you are fashioning it I just don't understand the mechanics.
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Torsion springs Thimo. Its like a bit bundle of sinew you stick a stick in and then twist up to store the energy. Then pull on the stick further to store more tension in it then let her go, WHAMO! Lot of torque to hurrel that thar bolt down range. One day I will definitely make one!
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I have recently watched a 6 part series called "Ancient Discoveries", that I got from the library. It was basically about the inventions of the classical world and how we should give them so much more credit for how advanced their technology and understanding of scientific principles was. Like the raw efficiency of the ballista's coiled rope springs. On the show, was even a reproduction of Heron of Alexandria's chain drive, repeating balista!
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Thimo, how Tiller described it is prettty much it.
Here is a shot of a catapult over in England that shows the rope springs pretty well, and the arrow in place and ready to fire.
Bows are springs, as are rope bundles, just different kinds. With a bow, you already have energy stored in the machine, and when you pull it back to full draw, create more energy. To fire the bow, you release the string with your fingers, the bow arms move forward, and your arrow shoots toward the target. In a catapult, you have two very tightly coiled skeins of rope, held in place at top and bottom by metal washers and tenons, as you can see in the photo. You hammer two bow arms through the center of the rope springs, and impart ever more energy in the springs by twisting them and locking them in place with pins through the washers that go into the wooden spring frame. You winch back the bow string by using a pawl and a rope and winch system, lock it back with a trigger mechanism, put your arrow in place, and fire it by releaseing the trigger pawl. All that stored energy fires the arrow with so much force, it is impossible to see with the naked eye.
If you are the target and happen to be holding a shield, it shoots through that like it wasnt there. If you happen to be standing by a tree, the arrow has enough force to pin you through the spine to the tree, as did happen in one historic battle. One Latin name for these kinds of machines is tormenta, which is almost poetic :)
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I have recently watched a 6 part series called "Ancient Discoveries", that I got from the library. It was basically about the inventions of the classical world and how we should give them so much more credit for how advanced their technology and understanding of scientific principles was. Like the raw efficiency of the ballista's coiled rope springs. On the show, was even a reproduction of Heron of Alexandria's chain drive, repeating balista!
Orc, I saw that too. And the repeating machine that Alan Wilkins and Len Morgan build is pretty cool. The History Channel also had a show about ancient super ballistics that Alan demonstrated the machine on. Here are two shots of one, I believe in a museum in Germany (but not certain) that show it pretty well. Not sure if this is the same machine, or another reconstruction.
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Okay, I have both inner stanchions riveted and blued. Some additional filing is necessary to get a better fit, as well as touch up to the rivet heads, but overall, I am pleased. The next step is to cut out the plating for the outer stanchions, the band that goes around the two hole carriers, and then the counter plates for the washers, which will be inset into place.
Dane
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Wasn't there some debat on how the arms where set up on these things?
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David, there continues to be. As for my work, I debated with some other catapult builders (ballistarie in Latin) about how the arms are positioned. One school of thought is that the end of the arms has to slam into the inner stanchion back edges to absorb the energy as you discharge the weapon. I feel strongly that the inner arms don't do that, but possibly do hit the outer facing sides of the inner stanchions (why I plated them), but mostly, the bow string absorbs the energy, much like a bow does. Under no circumstances do you want the arms to slam into the outer stanchion recesses (the half moon looking cutouts). That is a good recipe for cracked stanchions and arms.
That is not even touching on the inswinger vs. outswinger debate that is currently pretty hot. I can try to fill you in on that, but for the purposes of an arrow firing scorpion, called a Euthytone, they are always outswingers.
Okay, here is the basic formulaa for calibrating a catapult. It is D = 1/9 L, D being diameter, L being length of arrow.
I am not sure if they decided on the arrow length first, or the spring diameter first, but my 2" machine, using that formula, has an 18" long arrow. 2" x 9 = 18". Or I could have formulated it by wanting an 18" arrow, and dividing by 9", which comes out to 2" for the spring diameter. All other dimensions for the arrow firing machines are taken from the spring size. A 3" machine would fire a 27" arrow, and a 4" machine would have a 36" long arrow.
If you want, David, I can email you a complete set of dimensions for all parts of the catapult. It is pretty long, and there are two, an earlier set of dimensions set out by Philon, and a later set developed by Vitruvius, an engineer who worked for J. Ceaser himself. I'm uising the earlier set, hence my machine being a Republic / early Empire machine.
Dane
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Well, hi everyone. Here is the next installment. The spring frame is nearly done! I plated it with 16 gauge cold rolled steel, and it comes out to about 15 pounds now. I made homemade copper rivets, and getting a real anvil really helped there. One thing about working with steel is that no hardwood will feel as hard after that, :)
It was just slow but satisfying work. I used metal cutting saw blades with a regular power jig saw, and then lots of file work. I ended up painting all the metal work, as it would be almost a full time job keeping rust from forming on the plating, and I am pleased with how it turned out. I used brushed on metal primer, then hand painted the milk paint. The stuff is very easy to use, no fumes, but you have to be a bit cautious with it, as lime is an active ingredient, and it would not be good getting it in your eyes. I still have to put a finish on it, and am not sure what that will be yet. Probably spar varnish thinned with turpentine and then a beeswax coating over that.
Next step really is casting the bronze washers, and then making the rope. So, it is going relatively fast now. Fast is relative, as I am guessing the entire plating phase took 40 hours.
Attached are photos of the priming stage, and then a couple of the spring frame with red milk paint applied, about 3 coats so far. Any dings and such are actually okay, as this machine will represent a very old catapult that has been in Roman service for a long while out in Cyrenaica, which was a Roman province in North Africa. I am actually looking forward to how actual hard use will affect the machine. The frame really is like a little tank, it is so sturdy.
Dane
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Here is one more shot. Notice the two large nail heads on the ends of the hole carrier ends? Those were forged by Bob Patrick, and his work is just amazing. Catapults used a combination of nails and rivets to hold all the plating on the frames, so while I was not following an actual machine, I was following known practices in construction.
One of the most important things I was shooting for in this, my first ever sheet metal work, was good close fit to the wood, and clean lines. I think I did okay.
Dane
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Keep us posted on the progress! I've got a stash of oak 2 1/2x5's that i'm going to make one of these someday. I really liked seeing how the trigger mechanism works (from an earlier post of 3-D drawing). Good work!!
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Thanks, Orcbow. Any advice or documents or whatever if you decide to build one, don't hesitate to ask me about. Oak would be a fine choice of wood for building one of these things.
Dane
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It is rather the engineering and design rather than the springs themselves that produce the effeciency (transfer of energy).The rope bundles themselves are suspect to effeciency. In VG Harts paper, he compares the performance of two identical designs the outswinger ballista (greek) and inswingng (roman).
The inswinger coughted up a 48% greater range.
"Reviewing these figures we see taht it is relevant to note that the Hatra machine may be said to be more effecient that the Greek machine; indeed, since their missile kinetic energies at launch amount to 38% amd 30% of their respective strain energies. Also, spring friction represents 72% of total energy for the Hatra machine, and 78% for the Greek."
My work has involved improving the effeciencies of the machines, primarily through engineering. In as much as a recurve bow of eithe modern or primitive design represents a very high degree of effeciency by eliminating friction, I offer the test results of my little inswinger designs from a small ballista bow powered by a single extension spring providing only 18lbs of pull at full 26 inches of draw. Might I add that it is a simple compound design with two pulleys mounted on the end of each arm, the string looping around and coming back to the main chassis to ward the trigger assembly.
Velocities recorded for a 584 grain arrow was 30 mps, and 24 fps for a 974 grain arrow. While not horrifically fast, thats 32 grains per lbs of pull with the lighter arrow, and 54 for the larger arrow.
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author=orcbow link=topic=6909.msg118115#msg118115 date=1217760988]
I have recently watched a 6 part series called "Ancient Discoveries", that I got from the library. It was basically about the inventions of the classical world and how we should give them so much more credit for how advanced their technology and understanding of scientific principles was. Like the raw efficiency of the ballista's coiled rope springs. On the show, was even a reproduction of Heron of Alexandria's chain drive, repeating balista!
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Warhammer, this thread is almost 3 years dead.
I've checked out some of your ideas on RAT. While interesting, my interest in torision and tension machines is to try and replicate what ancient Romans and Greeks were building and using for military applications and finding out what kind of peformance they actually had, not what we can do with modern theories, construction, or material.
I seriously doubt that Heron or Vitruvius would have been building compound arrow machines. W
ith respect, I dont intend to go anywhere close to reengineering and "improving" ancient engineering. Leave that to Wilkins and his ilk.
Dane
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David, there continues to be. As for my work, I debated with some other catapult builders (ballistarie in Latin) about how the arms are positioned. One school of thought is that the end of the arms has to slam into the inner stanchion back edges to absorb the energy as you discharge the weapon. I feel strongly that the inner arms don't do that, but possibly do hit the outer facing sides of the inner stanchions (why I plated them), but mostly, the bow string absorbs the energy, much like a bow does. Under no circumstances do you want the arms to slam into the outer stanchion recesses (the half moon looking cutouts). That is a good recipe for cracked stanchions and arms.
The only reason arms would slam into the stanchions is if the string had no tension at rest, which would greatly increase effeciency and allow all available energies to be transferred to projectile. In this case, the stanchion has no choice than to act as a simple fulcrum, with the rope bundle absorbing the brunt of arm momentum, until the string lost its apparant slack. In the above example it is assumed it is a single stanchion machine, with no stanchion arresting movement of the arms "heel" (Aitor)
Doubting this, I invite you for next Orsova field trials where such an occurance happens regularly. 5000lbs of pull WILL stretch the rope out of shape temporarily. Or simply watch the videos.
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I am aware of the disdain in which my work is regarded. Nonetheless, my work has served its purpose in helping Nick attain his goals while improvement in performance using my engineering. Nick is way ahead of you guys, Marsden Wilkins etc. While I respect their contributions, certainly you must agree that they produce less than optimal performance in relation to performance reported in treatises.
In defence of their work though, they will serve well enough for outswingers, but clearly for inswingers my work is undesputable with reproducable results upon demand. Previous calculations for outswingers has NO place in inswinger engineering, but merely used as a reference or starting point.
Why else do you think I can argue with complete confidence with Mr. Harts contributions and pure research? Results are results. Solving the riddle of ballista performance is akin to solving the mystery of the pyramid construction. This I have accomplished, and am trying to share it. You are a hard headed lot for sure.
Is no the least bit curious in solving the performance calculations for the inswinger as they relate to outswinger formula's????? It sure sucks being a pioneer in the field for sure. With a grade ten education it has not been an easy task for sure, but nothing compared to the effort required to changed academic opinion and way of thinking. I do not blindly accept doctrine, and it is my nature to challenge accepted doctrine and methodology.
Yes I know this thread is three years old, but so calculations you use are a couple thousand. dont worry, my health is failing fast, and I have no help from the scientific community whatsoever. The ideas and concepts are all I wil be able to leave you guys, evidenced in help building the worlds fastest balista past or present. NOt even NIck understands my work but must accept the results as performance is his primary goal.
NIcks machine is only a stage one design. I am many years ahead of that, daring to challenge supersonic capabilities as a design challenge. A 500fps ballista will be my legacy to leave behind. Who knows maybe one day in a museum. I will walk my own path, and lead the way for the more bold . That will not stop me from admiring your work and craftmanship, and although my voice not welcome , will continue to voice my opinions and research where and when permitted.
I look forward to seeing more work from you.
If there is a more recent contribution regarding ballistas and pure science or research here or anywhere else, please let me know.
Warhammer, this thread is almost 3 years dead.
I've checked out some of your ideas on RAT. While interesting, my interest in torision and tension machines is to try and replicate what ancient Romans and Greeks were building and using for military applications and finding out what kind of peformance they actually had, not what we can do with modern theories, construction, or material.
I seriously doubt that Heron or Vitruvius would have been building compound arrow machines. W
ith respect, I dont intend to go anywhere close to reengineering and "improving" ancient engineering. Leave that to Wilkins and his ilk.
Dane
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Warhammer, you are probably a nice guy, and sincere, but you have to understand my perspective, which will not change in the case of Roman and Greek torsion and tension engineering. The whole point of researching the machines and building working interpretations of a Vitruvious or Heron machine is this: to understand the probable capabilities and performance of ancient artillery. Not what they may do if you reengineer them, but what a Roman army in 79 AD would have had as way of field artillery available in the then-here and now.
What you are doing, while it is important for you to break new ground, is contrary to what some of us are doing. An example would be to explore a medieval English yew war bow, but make it out of fiberglass, and replace clothyard arrows with fiber arrows. What do you gain? More performance than is possible with a 14th century bow, but if you are trying to understand what actual medieval bows could do, you learn nothing of historical value.
Another is to take a rifled musket reproduction from the US Civil War, glass bed the barrel, rework the trigger, replace the sights, and optimize the weapons in every other way possible. You have a much more accurate weapons than a soldier of 1863 would have had, but you don’t learn much about the accuracy and shooting characteristics of an actual weapon from that conflict.
The outswinger vs. inswinger battles – I agree with how much more effective inswingers are, and probably were much more prevalent in the ancient world than some think they were. Hartra had to be an inswinger, and it appears to be thus via Trajan’s column. Perhaps even all stone throwing machines in mid empire were inswingers. My own little machines are based on earlier machines, and I think outswinging configuration is fair and was probably the primary ways of setting up a scorpion. If I were to build a metal framed arrow machine, it would be most definitely an inswinger.
Purely improving performance of an ancient design is fine if that floats your boat, but the chances of Roman and Greek engineers having developed compound (wheels) technology is bordering on ridiculous (Kind of like SCA folks using duct tape and saying if they had it in the 14th century, they would have used it as way of justification). What you are doing is not engineering interpretations of ancient stone and arrow throwing machines, but something entirely different. I’m not really sure what the entire point of that is, as catapults and ballistas have been obsolete weapons systems for almost 2,000 years. Da Vinci did some fanciful sketches of theoretical war machines at a time when gun powder had doomed such weapons. Hence, they never got beyond design sketches.
Maybe you should focus on the pumpkin chuckers. Those guys are pushing catapult designs to the max, and you would feel right at home. The goal is to hurl a pumpkin 1 mile. I think they would welcome you with open arms. Google them, as there is tons of stuff online about what they do, videos, etc. Googling Team Tormenta will get you right to their site, if I recall. Nice group of folks, too.
Dane
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I know this is an old thread, I just wondered how it all turned out?
The skeins of rope should be made of horse hair or sinew for maximum power according to Sir Ralph Payne Gallwey.
I think linen thread is an alternative (that's what I used on my miniature seige engine).
Leather buffers stuffed with horse hair would seem like a good idea to absorb the arm impact.
The question of string tension is a V good one, I'd have though maybe share the tension between string and leather buffers, a completely slack string has got to be a bad idea.
I've seen a few TV show where they try to make Da Vinci style giant bows or suchlike (e.g Scrapheap Challenge) The usual mistake they make is a slack string which generally causes a broken bow when it bends the other way.
I did see one great prog' where they made a formidable Trebuchet which lobbed 300lb sandstone balls... ;D
Del
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Del, I stopped working on the two catapults as I marshalled my thoughts and reimagined how I was going to make various metal parts (triggers, washers, etc). Finally, I am set to get back to it, but it was yikes, two years ago that I stopped progress.
Horsehair was secondary in preference to the ancients, who felt sinew was the best rope material. I feel they are correct, but dig this, not one reconstructed catapult has ever been made with actual sinew rope. I'd like to tackle that one day, but the amount of sinew to make 300 feet of rope is formidable. One builder from the 19th century, Dr. Schramm of Germany, did use horsehair in his reconstrucitons. To the best of my knowledge, most of his machines were destroyed during allied bombing missions - maybe your boys on night raids, or ours on daylight raids.
"Gentlemen, todays mission is....German catapult reconstructions...." "Gulp!" "Blimey, this one will be rough." "Jezz, only one more mission and I get to go home....this aint gonna be a milk run."
One, a 3 span machine, apparently did survive the war.
So, no one today really does know how a Roman catapult may have behaved and performed. I do plan on making horsehair rope in an improvised ropewalk, but first the metal bits have to be completed.
Badger here on the forums was the bow expert for one of those shows, and he was on the show, Doing Da Vinci. You may want to ask him about his contribution. A weird circular bow powered stone thrower, if I recall right. It was just huge, that thing, and didn't perform particularly well, but not because of Badger's work.
Tribuchets are interesting, but hardly any one makes one to the huge sizes the medieval armies must have used. One show filmed in England had this landed gentry type fellow hurling small cars across his fields, and exploding fuel drums, as well. Boys will, of course, be boys.
Dane
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Badger here on the forums was the bow expert for one of those shows, and he was on the show, Doing Da Vinci. You may want to ask him about his contribution. A weird circular bow powered stone thrower, if I recall right. It was just huge, that thing, and didn't perform particularly well, but not because of Badger's work.
I just watched that episode on Youtube, it was quite interesting. I enjoyed watching Steve work, but really have to give him credit for not strangling that obnoxious "Flash" character. Too bad they didn't get better performance from that monster, but it was entertaining to watch the build.